This commit modifies the client's filtering when selecting from existing
sessions. The new logic compares the configured TxPolicy with the
TxPolicy of the candidate sessions, which has the effect of ignoring
operational parameters such as MaxUpdates. Prior, changing MaxUpdates
would cause the client to request a new session even if it had perfectly
good slots available in a policy with an equal TxPolicy.
This commit splits out the parameters that shape the justice transaction
into their own struct, which then embedded within the overarching
wtpolicy.Policy which may have additional parameters describing
operation of the session.
This is done as a preliminary step to support comparison of sessions
based on matching TxPolicy configurations. This prevents otherwise
identical Policies from being counted as different if operational
parameters like MaxUpdates differ, even if it has no material difference
to the justice transaction.
Now that the committed and acked updates are persisted across restarts,
we will use them to filter out duplicate commit heights presented by the
client.
